The densest layer (inner core) is at the center and the least dense layer (crust) is the outermost layer. The atmosphere, composed of gases, can technically be considered a layer as well and is obviously lighter than the crust.

Which compositional layer of the Earth is the densest?

Earth's interior layers are ordered by density. The densest layer is the solid metal inner core, the mantle is of intermediate density, and the least dense layer is the lithosphere, particularly the continental lithosphere.

Which layer of the Earth has highest density?

The solid metal inner core is the densest layer, the mantle is intermediately dense, and the lithosphere, particularly the continental lithosphere, is the least dense layer.